Laser applications in large area optical sensors and biomedical imaging

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This research focuses on methods of enhancing detecting arrays and their detection capabilities. These have the general connecting theme of being optically connected methods, especially those making use of lasers, in either sensor operation or fabrication. This program extends four projects started under my previous NSERC discovery grants. The first creates sensing arrays which are very immune to defects. This explores a set of methodologies such as the application of Fault Tolerant Active Pixel Sensors, software algorithms to detect defects and identify the defect type from images taken under normal operating conditions, and algorithms to recover array information from knowledge of the defect type. This enables the building of very large area sensor arrays (yield improvement) and extends imager lifetime, especially in hostile environments where failure rates are high. The second creates optical imagers, based on Active Pixel Sensor (APS) concepts, that allow detection in ways that existing imagers cannot. Previous APS research has pointed us to a number of new detectors: phase sensitive detection of encoded illumination, better resolution by removing the loss of APS sensitivity as pixels shrink below a few microns, expanding dynamic range for imagers, enhanced photogate APS' which, unlike current devices, are highly sensitive in blue light. The third explores a new approach, called Angular Domain Imaging, to optical tomography in scattering media such as tissue. This employs lasers and micromachined collimating arrays combined with optical imaging arrays to separate the highly scattered light from the unscattered or slightly scattered light which carries internal structural information. Unlike existing systems, this methodology lends itself both to highly scattering media of short distances (eg. medical imaging) and lower scattering over longer distances (fog, or turbid water). Finally in the previous NSERC discovery grant, we developed a new inorganic resist Bi/In, which oxidizes on laser exposure to a transparent conducting oxide. This laser direct write oxidation allows us to explore this material's application in electronic devices, such as new types of X-ray detectors and transparent transistors.